Ground-based Remote Sensing Observations of Atmospheric Trace Gases, Validation and Complementary Observations for Space-borne Sensors
A contribution to ACCENT-TROPOSAT-2, Task Group 3
University of Bremen, Otto-Hahn-Allee, 28334 Bremen, Germany
Long term observations of atmospheric trace gases on a global scale are an important part within ACCENT. The remote sensing group of the University of Bremen in cooperation with the Alfred-Wegener-Institute performs ground-based observations of atmospheric trace gases at several stations using the FTIR and microwave (MW) spectrometry. The FTIR-spectrometry allows us to measure the total column concentrations of about 20 trace gases. For a several of them the concentration profiles can be retrieved from the ground up to about 30 km with a vertical resolution of 4-8 km. The MW spectroscopy covers the stratosphere up to 60 km and complements the FTIR observations. FTIR and MW observations have been used successfully for the validation of satellite sensors. Furthermore, with their spatial and temporal resolution they increase the information content of the global satellite observations.
We propose to include the following observations within ACCENT-TROPOSAT-2.
Arctic: Ny-Ĺlesund, Spitsbergen (78°N); FTIR and MW since 1992.
Arctic: Summit, Greenland (72°N); MW since 2003.
Mid-latitudes: Bremen, Germany (53°N). FTIR and MW since 2000.
Ship cruises on the Atlantic (typically 50°N to 30°S), up to now 6 cruises since 1994.
Tropics: Merida, Venecuela (8°N) /Paramaibo, Surinam (6°N), MW started in 2004, FTIR is planned to start at the end of 2004.
Within the frame of ACCENT-TROPOSAT-2 we suggest to perform the following activities.
1. Perform measurements at all stations and analyse the spectra in a consistent way to enable the direct comparison of the results from all stations and with observations performed by other groups. Retrieve the total columns and concentration profiles of long-lived (CFC-12, CFC-22, SF6, CH4, N2O, CO2) and shorter lived trace gases (CO, C2H2, C2H6, CH2O, OCS, HCN, O3).
2. Derive the seasonal or latitudinal variabilities of tropospheric trace gas concentrations at the stations.
3. Investigate the variabilities at each station with respect to, for example, nearby local emission sources (Bremen), transport of biomass burning plumes and interhemispheric differences (ship cruises, Venecuela/Surinam), or long range transport of pollutants to remote areas (Spitsbergen, Greenland).
4. Interpret the data together with existing in-situ data (e.g. AGAGE, NOAA/CMDL) and satellite data (e.g. SCIAMACHY, MIPAS, MOPITT, HALOE, TES, ACE) considering the specifics of each station.
5. Form a common data set that can be used by models. Make the data set available to the public.
EC projects, national fundings, University funding. The activities will be part of existing projects (e.g. STAR, SOGE, UFTIR, RAMAS).
The activities proposed are expected to be continued on a long-term basis, covering the whole time period of ACCENT.
Justus Notholt, Thorsten Warneke and Harry Küllmann